Does the tax deadline April 17 include the day itself?

[taxguyask]

Let's say I send the return letter in last minute when my local post office closes at 8:00 pm on April 17.  The postmark on the envelope shows April 17 so it won't be counted as late filing?

[GlimmerofHope]

Hi,

As long as its is postmarked April 17th it wont be marked as late. 

Good luck!

Tia